1. Field of the Invention
The invention relates to a welding head for a looping machine comprising a bearing housing; several clamping jaws for fixing and actuating the leading strap section and the strap section lapping there-over during withdrawal and welding of the looping strap; a pressure plate on the upper side of the welding head, acting as a holder upon actuation of the leading strap section and the strap section lapping there-over during the welding job; and a welding device in the welding head for welding together the leading strap section and the strap section lapping there-over.
2. Background Art
A welding head of the generic type is known for example from DE 297 16 897 U1. Generally, welding heads of this type with welding tongues which become hot are conventional in the field of looping machines and have been used for years among others also by Applicant. In this case, several clamping jaws are provided, which are disposed one after the other in the strap running direction and are guided for displacement crosswise of the plane of the strap, serving to fix and actuate the looping strap. The clamping jaws are moved into their respective position by a cam disk control system.
The welding head further comprises a pressure plate which is guided for displacement in parallel to the looping plane and crosswise of the strap running direction; it is provided on the upper side of the welding head as a holder upon actuation of the leading section of the strap and the overlapping strap section during welding. A welding tongue to be inserted between the strap layers that are to be welded together is guided on the bearing housing in parallel to the pressure plate.
These prior art welding tongues pose the problem that the motion of insertion and deflection of the welding tongue into, and out of, its respective position must be controlled by a comparatively complicated mechanism.
On the one hand this is accompanied with complex mechanical and constructional implementation which negatively affects the cycle time that can be achieved by the welding head. On the other hand the welding tongue and its entire operating apparatus requires much space within the welding head, which means a fundamental drawback in the light of the multiplicity of movable components that are to be controlled in the welding head.
Proceeding from the prior art drawbacks, it is the object of the invention to improve the welding device of a welding head of the species such that a more compact design of the head itself and reliable welding of the looping strap are achievable by reduced mechanical requirements and less complicated implementation in terms of control technology during the manufacture and operation of the welding head.
This object is attained by the invention, according to which the welding device is a laser beam welding device which, in the welding head, acts on the strap sections to be welded together.
The invention implies a fundamental change in the kind of welding of the looping strap sections. While the prior art proceeds from a mechanical body which must be heated, directly contacting the strap sections to be welded together, the invention uses electromagnetic radiation in the form of laser beams. There is no longer any need of a mechanical component which is to be moved between the strap sections in a complicated wayxe2x80x94as mentioned above. Rather, the strap sections can be exposed to the laser beams, melted and durably united by the pressure of the clamping jaws directly after the looping job once the loop of the strap has been severed from the strap supply.
In accordance with preferred embodiments of the invention, the laser radiation as such can be produced for example by laser diodes which are disposed in the clamping jaws orxe2x80x94if sufficient space is availablexe2x80x94between these clamping jaws. Any complicated laser-optical guide elements can then be dropped. However, it is also conceivable to provide for a supply laser outside the clamping jaws within the welding head or at any other place of the looping machine and, via fiber-optical light guides, to supply the laser radiation to the strap sections to be welded together in the head. This may take place right through the clamping jaws or for instance via the pressure plate which serves as a holder.
Further details of the invention will become apparent from the ensuing description of exemplary embodiments, taken in conjunction with the annexed drawings.